I have read all the info on this and here is my dilema. I just purchased a speed up kit for my walker. I am just finding out now that it is the wrong kit, its for an MD not an MT #7246 and #8246 is what I need. Well the correct kit #8246 has the same pulley, the #7246 has the pulley and a belt. After going through the run around trying to make the belt fit it turns out you use the stock belt with the #8246 kit. Finally figured this out. Now I have seen talk of a heavier spring than stock. It does not come with the #8246. How do I get it?